The part may be a solid SiC part, or a part having a substrate that is not made of SiC and that is covered in an SiC layer. Parts comprising a substrate covered in an SiC layer are used in high temperature applications, i.e. applications for temperatures in the range 300° C. to 1100° C. By way of example, the substrate may be a ceramic matrix composite (CMC), i.e. a ceramic matrix reinforced by ceramic or carbon fibers, for example. The SiC layer is to give the part better resistance to oxidation and better mechanical properties at high temperatures. Because of these properties, such parts are used in particular in aviation turbomachines.
In certain applications, it is necessary for the SiC surface to have deposited thereon a coating, e.g. of metal or ceramic, such as mullite, cordierite, or zirconia. The coating is generally for the purpose of improving the high temperature strength or resistance to corrosion of the part on which it is deposited. Deposition can be performed either by atmospheric thermal spraying, or by means of a cement.
Typically, said coating is of alumina Al2O3. Alumina is deposited either by atmospheric thermal spraying of alumina (atmospheric plasma spraying of powder or flame spraying of a wire), or else in the form of an alumina-based cement, or indeed by a combination of those methods, which are well known in the state of the art.
Mechanical and thermal tests performed on parts having an SiC surface covered in an alumina coating show that the main mode of failure is rupture at the interface between the SiC surface and the alumina coating.
In order to improve the tenacity of the interface, modifications have been made to the state of the SiC surface. Thus, sand blasting (using compressed air to blow particles of alumina having a diameter of a few hundreds of micrometers) has been performed on the SiC surface in order to increase its roughness. Nevertheless, sand blasting leads to damage to the SiC surface without creating favorable roughness.
The present invention seeks to remedy those drawbacks.